Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.
-
Upload
joella-black -
Category
Documents
-
view
213 -
download
0
Transcript of Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.
![Page 1: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/1.jpg)
Short Course on Gullies and Streams
Tom Millard, Vancouver Forest Region
![Page 2: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/2.jpg)
Objectives
• Report on recent studies
• Provide an update on GAP changes
![Page 3: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/3.jpg)
Debris definitions
• Woody debris - “slash”
• Landslide debris - includes woody debris, rocks, soil, mud
• Debris flows and debris torrents - types of landslides
![Page 4: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/4.jpg)
Water transport of woody debris
• Woody debris floats downstream during floods
• Small WD easier to float than large slash• Flood may also transport small or moderate
amounts of sediment• Channel bed and banks remain relatively
unchanged• Occurs in any gradient channel
![Page 5: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/5.jpg)
Debris flow (or debris torrent)
• Debris flows almost always starts as a landslide into a gully channel
• Needs a steep channel to start in (>30%)
• Almost all wood and sediment is eroded - channel often scoured to bedrock
• Often no channel bed or banks remain
• Woody debris does not start a debris torrent
![Page 6: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/6.jpg)
History of GAP
• Started with a district request to identify gullies that would respond badly to logging
• Became a guidebook in 1995, first formal procedure for identifying different gully hazards and risks to downstream resources
• Recognized in 1995 that the procedures were preliminary and needed to be tested
• Studies undertaken from 1996 - 2000 have resulted in changes to the GAP
![Page 7: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/7.jpg)
Section 2: Water Transport Potential
![Page 8: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/8.jpg)
Water transport potential assessment
• Objective: to identify channels that will be disturbed if logged, or if woody debris is left in the channel.
• Disturbance: Erosion of channel banks and bed, woody debris jams, avulsions (breakouts), transport of woody debris into fish reaches
![Page 9: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/9.jpg)
No slash movement
![Page 10: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/10.jpg)
No slash movement
![Page 11: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/11.jpg)
Little slash movement
![Page 12: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/12.jpg)
Little - moderate slash movement
![Page 13: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/13.jpg)
Moderate slash movement
![Page 14: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/14.jpg)
Moderate slash movement
![Page 15: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/15.jpg)
Extensive slash movement
![Page 16: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/16.jpg)
Severe slash movement
![Page 17: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/17.jpg)
Severe slash movement
![Page 18: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/18.jpg)
Severe slash movement
![Page 19: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/19.jpg)
Old assessment method
ChannelGradient (%)
Channel Cross-section Area (m2)Channel width ____ (m) x Channel depth ____ (m) = XS Area ____ (m2)
____ CG < 0.5 0.5 - < 2 2 - < 5 5 - < 8 8 - <121
40 L M H H H20 - < 40 L L M H H8 - < 20 L L M M H
< 8 L L L M M
![Page 20: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/20.jpg)
Van. Island & Boston Bar Slash in Streams Studies
• Objective - to identify channels that become disturbed if slash is left in the channel after yarding is completed
• Channel disturbance = high water transport potential
![Page 21: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/21.jpg)
Vancouver Island study location
• Near Nitinat Lake, Southwest Vancouver Island
• Winter floods from rain storms
• Mostly rocky terrain, coarse grained soils
• “Nitinat”
![Page 22: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/22.jpg)
Boston Bar study location
• All streams located with Anderson River basin, east of Boston Bar
• Almost Interior conditions
• Snowmelt dominated floods
• Deep, fine-grained till soils
• “Anderson”
![Page 23: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/23.jpg)
Slash in Streams Study Methods
• Select streams logged 5 - 15 years ago, with the slash left in the stream
• Inventory amount and types of disturbance
• Collect data on width, depth, gradient, and other variables that may be used to predict disturbance
• Streams <5 m wide
![Page 24: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/24.jpg)
Disturbance
• Large sizes of woody debris transported
• Large amounts of woody debris transported
• Frequent and large woody debris jams
• Channel and bank erosion
![Page 25: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/25.jpg)
Severe disturbance
![Page 26: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/26.jpg)
Predictor variables
• Channel width and depth
• Gradient
• Channel location
• Channel and bank types
• Size of sediment moving
![Page 27: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/27.jpg)
Results
• Nitinat (Vancouver Island) study - 99 stream reaches
• Anderson River (Boston Bar) study - 42 stream reaches
![Page 28: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/28.jpg)
0
10
20
30
40
50
60
canyon fan gully openslope
valleyflat
Broadlyincised
Stream Location
Nu
mb
er
of
cases
Anderson
Nitinat
![Page 29: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/29.jpg)
0
5
10
15
20
25
30
0 - <10 10 -<20
20 -<30
30 -<40
40 -<50
50 -<60
>60
Gradient (percent)
Nu
mb
er
of
cases
Anderson
Nitinat
![Page 30: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/30.jpg)
05
10
1520253035
404550
0 - <1 1 - <2 2 - <3 3 - <4 4 - <5
Width (m)
Nu
mb
er o
f ca
ses
Anderson
Nitinat
![Page 31: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/31.jpg)
0
5
10
15
20
25
30
35
0 -<0.1
0.1 -<0.2
0.2 -<0.3
0.3 -<0.4
0.4 -<0.5
0.5 -<0.6
0.6 -<0.7
0.7 -<1.0
Depth (m)
Nu
mb
er o
f ca
ses
Anderson
Nitinat
![Page 32: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/32.jpg)
0
10
20
30
40
50
60
70
0 >0 - 0.001 0.001 -0.01
0.01 - 0.03 >0.03
Bank erosion (m3/m)
Nu
mb
er
of
cases
Anderson
Nitinat
![Page 33: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/33.jpg)
0
10
20
30
40
50
60
70
80
0 >0 - 0.001 0.001 -0.01
0.01 - 0.03 >0.03
Bed erosion (m3/m)
Nu
mb
er
of
cases
Anderson
Nitinat
![Page 34: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/34.jpg)
0
10
20
30
40
50
60
70
SWD LWD Logs
Size of woody debris moving
Nu
mb
er o
f ca
ses
Anderson
Nitinat
![Page 35: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/35.jpg)
0
5
10
15
20
25
30
35
0 0 -0.1 0.1 - 1 1 - 10 >10
Average Jam Volume (m3)
Nu
mb
er o
f ca
ses
Anderson
Nitinat
![Page 36: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/36.jpg)
0
5
10
15
20
25
30
35
40
45
0 0 -0.1 0.1 - 1 1 - 10 >10
Average Sediment Wedge Volume (m3)
Nu
mb
er
of
cases
Anderson
Nitinat
![Page 37: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/37.jpg)
Significant predictors of channel disturbance
• Channel width, depth, and area - width is best
• Size of sediment transported in the stream
![Page 38: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/38.jpg)
Channel width and size of woody debris moved
Channel width (m)Anderson Nitinat
Woodydebris size
moved Min. Median Max Min. Median MaxSWD 1.1 1.6 2.8 .8 2 3.3LWD 2.2 2.9 5.7 1.9 3 4.6Logs 4.9 3.1 4.1 5.8
![Page 39: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/39.jpg)
Jam volume and width: Nitinat
0
10
20
30
40
50
60
70
80
0 1 2 3 4 5
Channel width (m)
Avera
ge j
am
vo
lum
e (
m3)
![Page 40: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/40.jpg)
0
1
2
3
4
5
6
7
8
0 1 2 3 4 5
Average Channel Width (m)
Ave
rag
e ja
m v
olu
me
(m3 )
Jam volume and width: Anderson
![Page 41: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/41.jpg)
Sediment size and woody debris size moving
Sediment size moved (mm)Woody debris sizemoved Anderson Nitinat
Min. Median Max Min. Median MaxSWD 1 100 120 2 90 280LWD 110 200 310 45 150 360Logs 340 140 210 360
![Page 42: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/42.jpg)
Jam volume and sediment size: Nitinat
0
10
20
30
40
50
60
70
80
0 50 100 150 200 250 300 350 400
Maximum sediment size moved (mm)
Avera
ge j
am
vo
lum
e (
m3 )
![Page 43: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/43.jpg)
Jam volume and sediment size:Anderson
0
1
2
3
4
5
6
7
8
0 50 100 150 200 250 300 350 400
Maximum sediment size moved (mm)
Avera
ge j
am
vo
lum
e (
m3 )
![Page 44: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/44.jpg)
What about gradient?
• Gradient has no real effect
• Steeper streams have more channel roughness
• Lower gradient streams are more able to float woody debris
![Page 45: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/45.jpg)
Useful predictors of water transport potential
• Channel width (could also use channel area, but no better)
• Size of sediment moving in channel
• In these two studies, size of woody debris moving in channel was used as an response variable, but - can also be used as a predictor prior to harvesting
![Page 46: Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region.](https://reader030.fdocuments.in/reader030/viewer/2022013012/56649e0f5503460f94af9f98/html5/thumbnails/46.jpg)
Water transport assessment and cleaning strategies
Water transport potential Low Moderate HighBankfull channel width (m) < 2 > 2 - < 3.5 > 3.5Size of water transported woody debris SWD LWD LogsLargest sediment transported (mm) < 100 > 100 - < 200 > 200
Water transport potential Cleaning strategyLow Do not cleanModerate Clean all introduced SWD and most LWDHigh Clean all logging debris except larger logs